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Learning as I go on this CNG factory cummins converted 6bt natural gas unit.

I am checking the valves today and wondered if anyone could guide me on how to find TDC on a 6bt..
There is no injection pump .. there is an inspection window on the face cover with a mark but that would apply to IP motors I would assume.

Would there be a TDC mark in the bellhousing like some have?

kind of stumped here for a bit. I could rotate the motor and watch the valves
bit I'd like to be more accurate and find a mark if there is one.

In the pic below you can see the cover and where the little window is but like I said.. don't think it will aplly to a CNG unit. Instead of an IP there is an electronic unit bolt where the IP was.

thanks
Dr Loot
 

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On the back side of the timing cover, almost against the block should be a little plastic peg. As you are slowly turning the engine over by hand push in on the peg and it will pop into a hole on the back side of the cam gear right at TDC. Be careful not to break it.
 

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If the timing indicator isn't there, or if it's broken off (it's plastic..) you could always do the old trick of pulling the #1 spark plug and using a long stiff piece of wire.

Get the valves closed on #1, then stick the stiff wire down the hole. Rock it back and forth, and the point where the wire is sticking out of the hole the furthest is TDC.


Might even find the marks that way. (I tend to do this the first time I lay hands on a "new to me" engine so that I KNOW the marks can be relied on..)
 

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You might also pull a valve cover and find when the companion cylinder is rocking. jeremy
 

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He said "spark plug":)
 

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Like was said should be on the backside where the injection pump would've been, it's a little push in pull out plug and I suggest pulling it all the way out and using an inspection mirror to find the marking hole.
 

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Thanks for the replies...

No magic plug on the back of the timing cover.. there is room but
no plug. Did it the old fashioned way and pulled the valve covers and watched the valve movement.
Runs like a champ now.
BTW Kind of interesting ... this 6bt has a nice air compact compressor located under where the IP would be. Puts out 180 psi and when it reaches max psi the pump pushes the extra air into the intake. On the back of the Compressor there is a hydraulic pump that runs the cooling fan...kid of cool
Would make for some interesting swaps where one might need to relocate a radiator.

Thanks..
 

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Maybe a future you-tube video possible?
 

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I believe 6bt natural gas engines do have spark plugs.
See: http://www.everytime.cummins.com/assets/pdf/4103877.pdf

BTW, look at the hp/tq ratings at 1600 RPM. Maybe a good high MPG engine if swapped into an older pre emissions pick up truck. OOPS - I just made the price of Cummins CNG engines jump!
 

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well, I'll be a son of a gun. The compression ratio is quite low, isn't it? So it's not a diesel engine then...
 

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CNG = Compressed Natural Gas

Currently, 10-2012, CNG is priced locally at $1.96 gge (gasoline gallon equivalent), versus $3.96 gal diesel.

Have found several companies online that sell conversion kits, and many sources of instructions for rebuilding B series engines for CNG usage. Will be rebuilding my 6bt to run CNG, mostly lowering compression to 12:1 - 14:1 and replacing injectors with spark plugs.
 

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A very important area of the CNG gasoline technique would be the CNG reservoir or even cylinder. This specific works because the gasoline reservoir in which the CNG will be stashed till it can be employed by the actual serps.
________________
CNG Cylinders
 
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